Apparatus for casting multi-layer composite film

ABSTRACT

A(N END-FEED) DIE PLUG AND INLET BLOCK FOR A PLASTIC EXTRUSION MACHINE FOR CASTING MULTI-LAYER FILMS. ONE EMDODIMENT OF THE DIE PLUG IS A GENERALLY V-SHAPED GUIDE MEANS THAT RECIEVES A PORTION OF THE PLASTI MELT INTO THE ENCLOSED PORTION THEREOF AND ANOTHER PORTION ON THE OUTSIDE SO THAT THE FIRST PORTION FORMS AN INNER LAYER AND THE OTHER PORTIONS FORMS SURROUNDING OUTER LAYERS OF A COMPOSITIE MULTI-LAYER FILM. A SECOND EMBODIMENT OF THE (ENDFEED) DIE PLUG IS A PREDETERMINABLY OFFSET PLANAR GUIDE MEANS DIRECTING PLASTIC MELTS TO A DIE MEANS IN PRESELECTED THICKNESS RATIOS FR A TWO-LAYER COMPOSITE FILM. THE INLET BLOCK IS PROVIDED WITH ONE PASSAGEWAY FEEDING MELT ALONG A STRAIGHT LINE PATH INTO THE MEANS AND ANOTHER PASSAGEWAY FEEDING MELT AT AN ACUTE ANGLE TO THE STRAIGHT LINE PATH SO THAT THE PLASTIC MELT PASSING THROUGH THE SECOND PASSAGWAY FEEDING MELT AT AN ACUTE ANGLE TO THE STRAIGHT LINE THROUGH THE FIRST PASSAGEWAY.

Oct. 2, 1973 O STAFFORD Re. 27,769

APPARATUS IIUH CASTING MUIE'I'I IIAYI-IH (IOMPOfRI'III IIHIM OriginalFiled June 1, 1968 4 Sheets-Sheet 1 5 7! PM) ,2 FIG. I (PRIOR ART) I3 5\IO F I I I f *1 \*--I- I I I FIG. IA (PRIOR ART) Z8 M [B FIG. IB (PRIORART) FIG. 2 PRIOR ART 24 -D/I5 OIP/FICE WIDTH a gh FIG. 2B (PRIOR ART)Oct. 2, 1973 L Q STAFFORD Re. 27,769

APPARATUS FOR CASTING MUl/Il LAYI'IH COMPOSITE FILM Original Filed June4, 1968 4 Sheets-Sheet 2 522L53 5 3 5 is L g \A I A.) 54 C DIE OR/FICEWIDTH F 6. 5C

Oct. 2, 1973 O STAFFORD Re. 27,769

APPARATUS FOR CASTING MULTI IJAYF-R COMPOSITE FILM Original Filed June4, 1968 4 Sheets-Shem 5 6O 6a mbVOa i WLVB L AW FIG. 5A

. 1973 1.. o. STAFFORD Re. 27,769

APPARATUS FOR CASTING MULTI-LAYER COMPOSITE FILM Original Filed June 4,1968 4 Sheets-Sheet 4 United States Patent Ofice Re. 27,769 ReissuedOct. 2, 1973 27,769 APPARATUS FOR CASTING MULTI-LAYER COMPOSITE FILMLarry O. Statford, Beloit, Wis., assignor to Beloit Corporation, Beloit,Wis.

Original No. 3,583,032, dated June 8, 1971, Ser. No. 734,335, June 4,1968. Application for reissue Feb. 9, 1972, Ser. No. 224,762

Int. Cl. B29c 27/14 US. Cl. 425131 13 Claims Matter enclosed in heavybrackets appears in the original patent hut forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A[n end-feed] die plug and inlet block for aplastic extrusion machine for casting multi-layer films. One embodimentof the die plug is a generally V-shaped guide means that receives aportion of the plastic melt into the enclosed portion thereof andanother portion on the outside so that the first portion forms an innerlayer and the other portions form surrounding outer layers of a composite multi-layer film. A second embodiment of the [endfeed] die plugis a predeterminably offset planar guide means directing plastic meltsto a die means in preselected thickness ratios for a two-layer compositefilm. The inlet block is provided with one passageway feeding melt alonga straight line path into the die means and another passageway feedingmelt at an acute angle to the straight line path so that the plasticmelt passing through the second passageway reaches the die outlet priorto the melt passing through the first passageway.

The present invention relates to improvements in plastic film extrudersand more particularly, to a[n end feed] die plug inlet block arrangementfor a multi-layer composite film extruder.

In a plastic extruder of the type conventionally used, the plasticmaterial or melt is delivered along an extruder barrel by an extruderscrew into an inlet and through a die plug into a die means for castinginto a desired shape. One conventional type of die plug is a center-feeddie which permits a limited degree of success but nevertheless has anumber of substantial drawbacks. For example, when a center-feed dieplug is utilized in extruding a three layer film, an uneven distributionof materials in the center layer results, yielding unwanted variationsin the uniformity of physical characteristics of such a film. Anotherconventional type of die plug is an end-feed die plug which alsoexhibits a limited degree of success but also has a number of drawbacks.For example, while a con ventional end-feed die plug produces a somewhatmore even material distribution within a three layer film than acenter-feed die plug, it fails to provide a uniform flow rate throughoutan elongated die and thereby necessitates the utilization of relativelyshort die means producing relatively narrow film widths.

It is accordingly an object of the present invention to provide animproved [end-feed] die plug arrangement for a film extruder whereinrelatively long die means can be utilized having substantially uniformmaterial distribution in the formed multi-layer film and substantiallyuniform flow rates along all portions of the die means.

A further object of the invention is to provide an improved plastic meltdelivery arrangement for an elongated die means using a novel [end-feed]die plug and inlet block to obtain substantially uniform flow ratesalong the die means.

Still another object of the invention is to provide an improved[end-feed] die plug which is readily removable and exchangeable foranother end-feed die plug without the necessity of cleaning the die andextruder apparatus.

Yet another object of the present invention is to provide an improvedend-feed die plug for use with a die means in an extruder producing atri-layer composite film having a substantially uniformly formed centerlayer and outer layer of relatively greater width than heretoforepossible.

A still further object of the invention is to provide an improved[end-feed] die plug for use with a die means in an extruder producingtwo-layer composite film having substantially uniform material flowrates along the die means.

Other objects, advantages and features will become more apparent withthe teachings of the principles of the preferred embodiments thereof inthe specification, claims and the drawings, in which:

FIG. 1 is a diagrammatical end view taken substantially along line II ofFIG. 1A illustrating a conventional center-feed die plug and die means;

FIG. 1A is an essentially diagrammatical side view of the center-feeddie plug, die means and the film formed thereby;

FIG. 1B is a diagrammatical cross-sectional view taken substantiallyalong lines IBIB of FIG. 1A illustrating a portion of the film;

FIG. 2 is an essentially diagrammatical elevational side view takensubstantially along line II-II of FIG. 2A illustrating the conventionalend-feed die plug and die means;

FIG. 2A is an essentially diagrammatical elevational side view of aconventional end-feed die plug, die means and film formed thereby;

FIG. 2B is a diagrammatical cross-sectional view taken substantiallyalong lines IIB-IIB of FIG. 2A illustrating a portion of the film;

FIG. 3 is an essentially diagrammatical elevational view, with parts inphantom, illustrating a portion of a film extruder constructed andoperated in accordance with the principles of the instant invention;

FIG. 3A is a diagrammatical end view taken substantially along linesIIIA'IIIA of FIG. 3 illustrating a portion of the plastic melt flow pathwithin the die means;

FIG. 3B is a diagrammatical end view taken substantially along linesIIIB-IIIB of FIG. 3 illustrating a further portion of the plastic meltflow path within the die means;

FIG. 3C is a diagrammatical cross-sectional view taken substantiallyalong lines IIIC-IIIC of FIG. 3 illustrating a portion of the compositefilm flow in accordance with the principles of the present invention;

FIG. 4 is an essentially diagrammatical elevational front view takensubstantially along lines IV-IV of FIG. 4A, illustrating an embodimentof the end-feed die plug of the present invention;

FIG. 4A is an essentially diagrammatical elevational side view of aportion of a plastic film extruder constructed and operating inaccordance with the principles of the present invention;

FIG. 4B is an essentially diagrammatical top view taken substantiallyalong lines IVBIVB of FIG. 4A illustrating additional features of theplastic film extruder of the present invention;

FIG. 5 is an essentially diagrammatical front view, with parts onphantom, illustrating another embodiment of the end-feed die plug of thepresent invention;

FIG. 5A is an essentially diagrammatical elevational side view takensubstantially along lines VA-VA of FIG. 5 illustrating a portion of theplastic film extruder constructed and operating in accordance with theprinciples of the instant invention;

FIG. 6 is an essentially diagrammatical side view, with parts inphantom, illustrating the plastic melt feed system within a portion ofan inlet block constructed and operating in accordance with theprinciples of the instant invention; and

FIG. 6A is an essentially diagrammatical front view with parts inphantom, taken substantially along lines VIAVIA of FIG. 6 illustratingadditional features of the plastic melt feed system within an inletblock of the present invention.

FIG. 7 is a perspective view of the inlet housing block and die plugbuilt in accordance with the present invention.

As shown in the drawings:

FIG. 1 illustrates die means 10 having a center-feed [end] plug 11substantially in centroidal position of an elongated die means 10feeding plastic melt to said die means 10. The center-feed plug 11 isprovided with two substantially parallel guide means 12 which divide dieplug 11 into two outer chambers, 13 and 13a respectively, and an innerchamber 14. Plastic melt coming from appropriate supply sources issegmented into the respective chambers and thereby forms a multi-layeredfilm.

The mechanics of delivering a plastic melt to a die plug is wellunderstood in the art and need not be explained further.

FIG. 1A shows a die means 10 having a center-feed plug 11 substantiallyas explained hcreinbefore which allows the tri-layer film to expand intoan elongated die slot 15 and exit therefrom to form a film 16. Q and Qdesignate the flow of plastic from the respective ends of the die slot15 to a point where the curved edges of the film approach asymptoticallyto a line perpendicular to the orifice of the die means. These flowrates are utilized to determine the suitability of any particular typedie in producing a useable film and will be explained hereinafter ingreater detail.

FIG. 1B shows a cross-sectional view of a portion of the film formed bya center-feed die plug, such as illustrated at FIG. 1. The film 16 hasone outer layer 17 and another outer layer 18 with a center layer 19therebetween. Layers l7 and 18 are generally the same material whilelayer 19 may be the same material or it may be of a ditferent material.As will be noted, the ends of the formed film produce dimples 17a and18a respectively in their particular layers and produce a bulge 19a inthe centroidal portion of center layer 19. Of course, to produce auseable film, the same must be trimmed to exclude the dimples 17a and18a, however, there is no such simple mechanical means for correctingthe bulge 19a, which of course produces undesirable variations in thephysical characteristics of the film. Thus, while a center-feed dieproduces substantially uniform flow rates Q and Q it fails to provide auniform distribution of material and is therefore generally consideredto be inferior to an end feed die plug.

As indicated hereinbefore, it is important that the flow rates Q and Q;are substantially equal to each other in order to achieve a uniformproduct. The ratio of Q to Q is generally known as the uniformity indexE. Uniformity index E must be greater than or at least equal to 0.98 inorder to have a commercially acceptable cast film. If such standards arenot adhered to, undesirable wrinkles or variations in film thicknessdevelop. As might be expected from the physical configurations, thecenterfeed die generally has a higher uniformity index than an end-feeddie of equal length, if all other factors are also equal. In fact, acenter-feed die could theoretically be twice as long as an end-feed dieand still have the same uniformity index. However, because of thenon-uniformity of the sheet produced with a center-feed die, [and] anend-feed die is preferred, even though a shorter die must be utilized inorder to bring the uniformity index within the desired limits.

FlG. 2 illustrates a conventional die means 20 having a housing 21 whichis adapted for mounting a conventional end-feed die plug 22 therein. Theend-feed die plug 22 is provided with two substantially parallel andvertical guide means 23 segmenting the die plug [25] 22 into outerchambers 24 and 24a and an inner chamber 25 [22] with all said chamberscommunicating with an outlet slot 26.

FIG. 2A shows a side elevational view of die means 20 having housing 21and end-feed die plug 22 mounted therein. End-feed die plug 22 feedsplastic melt into an elongated passageway 27. Passageway 27 forms achamber within die means 20, which chamber feeds the plastic melt downthrough a die slot (not shown). The plastic melt exists from the dieslot and forms a film 28, and, as will be noticed, the flow rates Q andQ are not equal. In order to produce a substantially useable film withthis type of die plug, it is necessary to trim the film 28 to a width Wto eliminate the various material unevenness within the composite film.As will be noticed, only about 70% of the cast width is actuallyutilizable.

FIG. 2B shows a crosssection of the cast film 28 having outer layers 29and 31 and an inner layer 32. It will be noted that dimples 29a and 31aare formed only on the far side of the film and that the near side ofthe film produces a bead 32a. The central portion of the film issubstantially uniform. In order to reduce all variations within thisfilm it is necessary to trim off a substantial portion thereof, so thatmuch waste and relatively narrow film widths result.

FIG. 3 generally illustrates the detachable inlet housing portion a anddie means [of an extruder 40] utilizing the principles of the instantinvention. [Extruder] housing 40a is provided with a first supply means41 and a second supply means 42 feeding plastic melt from an appropriatesource (not shown) to an inlet chamber 41a, the inlet chamber beingdefined by the interior peripheral walls of the housing means. Theplastic melt in passages 41 and 42 may be the same or may be differenteither in chemical composition or in physical characteristics, i.e. havedifferent optical properties, such as color. The actual plasticmaterials utilized to form the film can be any conventionalthermoplastic materials such as, for example polypropylene andpolyethylene. As is well known, polypropylene is more abrasion resistantwhile polyethylene is more flexible so that by a proper combination ofvarious thickness of these two materials a wide variety of useable filmcan be obtained. The proportionate thickness of the inner and outerlayers of a particular film are varied in accordance with the ultimateuse of that film. Common uses for such composite film is in pouches forfrozen foods which are prepared by dropping the plastic pouch intoboiling water, packaging for hard candy, bread, wrappers, etc.

The plastic melt within inlet chamber 41a does not actually intermix butforms separate layers thereof which are forced through a die plug 43 inthe direction of the arrows shown. Die plug 43 has a guide means (notshown), but which are similar to guide means 65a [65b] (best seen atFIG. 7 [4]) separating the plastic melt into three individual contiguouslayers or streams (best seen at FIGS. 3A and 3B), which are fed outtoward cross machine straight line die passageway 45 and out of the dieopening 45a 0r slot to form a [composie] Composite film structure 46. Aswill be noted, a portion of the material leaving the end-feed die plug43 also exits out of a relatively short outlet feed passageway 44, whichis at an acute angle to the straight-line passageway 45 so that thematerial exiting through passageway 44 reaches slot[s] 45a prior to thematerial exiting from the straight line passageway 45. This is animportant feature of the invention as it eliminates the formation ofundesirable beads, such as shown at 32a in FIG. 2B which result fromconventional inlet blocks and die plugs. As will be appreciated, theplastic melt is simultaneously forced along a straight linesubstantially commensurate with the machine width of the die passageway45 and then downwardly along the machine length thereof through the slotopening 45a so that the plastic melt within die passageway 45continuously has two forces exerted against it, i.e. the cross-machineforce feeding new plastic melt into the chamber and the downward forceforcing the plastic melt out of the die slot 45a. Both of these flowrates must be substantially equal in order to achieve uniform flow rateand uniform distribution of materials within the compo-site film.

The unique die plug of the instant invention provides flow paths whichreadily achieve such uniform flow rates and material distribution withinthe composite film. FIG. 3A illustrates the plastic flow streams, incross-section immediately after passing end-feed die plug 43. It will benoted that the center stream or layer 51 is generally V-shaped and has across-sectional axes along the upper portion thereof greater thancross-sectional axes of the outer streams or layers 49 and 49a at asimilar location. The continuous boundaries of layers 49, 51, and 49a,[51] respectively of the plastic melt are generally tapered downwardlyin the annular passageway 44 by an exemplary form of guide means withinthe die plug 40a, said guide means being similar means 650 in FIG. 7.[48] [toward the slot opening and the angular outlet feed passageway44.] The angular passageway 44 allows the materials long the outerlayers 49 and 49a to reach the die slot 45a somewhat prior to thecentral layer 51 reaching the die slot 45a. As the material progressesdownwardly (i.e. along the machine length) along die passageway 45 ofFIG. 3, the center layer 51 expands along its upper portions (best seenin the change 0 boundary lines 48 at FIGS. 3A and 38) thereof inresponse to the pressure forces acting on it and insures that sufficientmaterial is present in the center layer 51 when it reaches the far endof the die passageway 56 and thereby enables it to form a uniform layerin the composite film 46.

The outer layers 49 and 49a are forced into smaller cross-sectionalareas within the die passageway and are therefore also forced out of dieslot 45a uniformly along the die axes. The V-shaped configuration of thecentral melt flow path insures that the material in the center portionmaintains suflicient pressure enabling it to uniformly exit through thelength of the die slot. It will thus be seen that supply means 42 feedsa plastic melt at a rate somewhat greater than the rate of material fedby feed means 41 and that the ratio of cross-sectional areas of I theV-shaped flow stream is somewhat less, at least initially, than thecross-sectional area of the flow streams surrounding said V-shaped flow[and] stream. In other words, the ratio of cross-sectional areas of theV-shaped flow stream to the cross-sectional area of the flow streamssurrounding said V-shaped flow stream is somewhat less than the ratio ofvolume flow rates of material being supplied from the first feed means41 feeding said V-shaped flow path to that being supplied by the secondfeed means 42 feeding the outer flow streams somewhat surrounding theV-shaped flow streams.

FIG. 3C illustrates a cross-sectional view of the composite film 46formed in accordance with the instant invention. The film 46 has outerlayers 53 and 54 and an inner layer 55 which is substantially uniformlydistributed throughout the width of the film, including at ends 55athereof. It will be noted that the outer layers 53 and 54 maintain theirdimples 53a and 54a respectively but that such dimples are less severethan that produced by the prior art methods. As indicated on thedrawings, the outer boundaries of the film substantially coincide withthe die orifice width. In accordance with the principles of the instantinvention, it is possible to utilize substantially greater width dieswith end-feed die plugs than heretofore possible. A preferred width of adie is 54 inches, although other die widths may also be useable. Theportions S at either end of the film 46 is trimmed and scrapped aswaste, however, this only amounts to approximately 5 to 10% of theoverall film width so that a useable portion W equals to of the castfilm width. For general purposes, a composite film structure of thistype is cast with an overall thickness of approximately 1 mil, whichoverall thickness is, of course, divided between the three layers inaccordance with the desired properties of the film. Thus, for example,when producing a composite film having an outer layer of polyethyleneand a center layer of polypropylene for use as boiling pouch materialfor packaging frozen foods, a suitable end-feed die plug of theinvention is selected (or adjusted) to provide a thickness ratio of thelayers substantially equal to 0.5:2.0:0.5. When such a composite film isproduced for use as a hard candy packaging material, a differentend-feed die plug is selected (or adjusted) to provide a thickness ratioof the layer substantially equal to 0.5:l.5:0.5 and if such a compositefilm is intended for use as a bread wrapping material, a furtherend-feed die plug is selected (or adjusted) to provide a thickness ratioof the layers substantially equal to 0.1 :0.8:0.1.

FIG. 4 illustrates an end-feed die plug 60 of the instant inventioncapable of handling two incoming streams of plastic melt to produce acomposite film consisting of an inner layer of one plastic surrounded oneither side by a layer of another plastic. The end-feed die plug 60comprises [a housing means 61] an annular outer housing portion orflange 70b having a plurality of fastening means 62 adapted for mountingon an inlet block (not shown) as to be secured thereto and [has an innerchamber 60a] the inlet block has interior walls defining a chamber 60a(FIG. 7). A first feed means 63 and a second feed means [65] 64 aredisposed to feed plastic melt to substantially opposed sides of the dieplug 60. Divergent melt guide means or vanes 65a are mounted within thechamber 60a to segment or divide chamber 60a into a plurality ofpassageways. The first or central melt or passageway 65 defines a firstinlet means generally centrally feeding plastic melt into a die chambermeans (not shown) tapered toward the outlet slot of such die chambermeans while the outer passageways 66, 66 define a second inlet meansfeeding plastic melt to the die chamber means generally around thecentral passageway 65. It will be noted that the central passageway orfirst inlet means 65 communicates only with the first feed means 63while outer passageways 66, 66 communicates with only the second feedmeans 64. Vane means 6521 are provided with a throat stop means 65bpreventing material in chamber 65 from passing therethrough.

As will be appreciated, the material is first fed into passageways 65and 66 until these passageways are completely filled and then thecontinued forced feeding forces the plastic melt in such passagaways topass in a plane generally perpendicular to the plane of the drawing andoccupy the width of a die chamber within a die means (not shown) andthen exit through a die opening slot therein. The divergent vane means65a generally form a V-shaped gate within the chamber 60a and aresubstantially rigid. It is contemplated that a plurality of such endfeed die plugs are provided so that each die plug has divergent guidesurfaces 65a that define a larger angle a therebetween, and such angleor ranges from about 15 to about thereby allowing an end user topreselect a particular die plug suitable for the thickness ratio of thelayers in a selected film. The divergent vane means preferably denesubstantially equidistant chords and define a plurality of inletchambers within the chamber 60a. In addition, it will be noted that thecross-sectional area of the central passageway or inlet means 65 issomewhat smaller than the total cross-sectional area of the outerpassageways 66 but that the central passageway has a largercross-sectional axis than the outer passageways. By this arrangement itis possible to provide somewhat greater fluid pressure with the upperportion of the central plastic melt than along similar upper portions ofthe outer plastic melt thereby forcing the outer plastic melt toward theoutlet slot of a die means at a constant rate while allowing the centralplastic melt to gradually expand into a greater cross-sectional area.Thus, when a greater volume flow rate of plastic melt is fed into thecentral passageway 65 than to the outer passageways, the fluid pressureis further increased and allows the central plastic melt to occupy thecentral portion of a die slot along its entire length and thereby exitas a substantially uniform central length and thereby exit as asubstantially uniform central layer in a composite film. In other words,the ratio of the cross-sectional area of the central inlet means 65 tothe cross-sectional area of the outer inlet means 66 is less than theratio of volume flow rates in the central inlet means or passagewayljs]65 to the volume flow rate in the outer [passage] inlet means orpassageways 66.

[Referring now to FIG. 4A wherein an inlet block means 70 having anelongated die means '71 attached to a housing 700 is illustrated. Diemeans 71 is provided with an elongated bottom outlet slot 72 whichcommunicates with the interior of the die means 71. The die means 71 islikewise provided with a first inlet passageway 63 and a second inletpassageway 64 feeding molten, normally solid thermoplastic resins orplastics which may or may not be the same depending upon the particulartype film being cast. The die means 71 is also provided with an end-feeddie plug 60 substantially similar to that explained hereinbefore. Dieplug 60 has a centrally disposed passageway 65 directing the plasticfrom feed means 63 into the centroidial position within die means 71 andout opening 72. The die plug 60 is likewise provided with outerpassageways 66 directing the plastic melt from feed means 64 intosurrounding relationship around the plastic being fed out of feed means64. The housing 700 is of conventional structure and need not bedescribed further.

Referring now to FIG. 4B wherein a top view of the inlet means 70 isillustrated. Inlet means 70 is provided with a housing 70a having anelongated die means 71 attached thereto. Die means 71 is provided with abottom outlet slot 72 for casting various thicknesses of film. Anend-feed die plug 60 is provided between the housing 70a and the diemeans 71 in order to segment or divide various plastic melts intoseparate layers so that a composite multi-layer film may be cast. Theend-feed die plug 60 is provided with outer passageways 66 and an innerpassageway 65 for producing a three-layered film. It might be pointedout that die means 71 is of relatively short cross-machine width assubstantially no waste occurs in the casting of multi-layered films,i.e., very little trim needed since non-uniform beads and the like areavoided whereby substantially the entire width of the cast film may beutilized] As best seen in FIGS. 4A, 4B and 7 die plug 60 comprises anannular outer housing portion or flange 70b, a main housing portion 700and the flow divider portion 70c, the flow divider portion beingcomprised of the divergent guide vanes 65a and throat stop means 65b. Atthe bottom of the flow divider portion 70c, the guide vanes 650 are inspaced relation and define an outlet slot 72 in a downstream directionrelative to the inlet passageways 63 and 64. Die plug 60 is similar todie plug 43 shown in FIG. 3.

FIG. illustrates another embodiment of an end'feed die plug 80 of theinstant invention capable of handling two incoming streams of plasticmelt to produce a twolayered composite film structure havingpre-selected thickness ratios of one plastic melt to the other. Theend-feed die plug comprises [a housing means 81] an annular housingportion 79a having a plurality of fastening means 82 adapted formounting on an inlet block (not shown) as to be secured thereto. The[end-feed die plug 80] inlet block has an inner chamber [80a] receivingtwo different plastic melts (although they could be the same) from afirst feed means 83 and a second feed means 84 feeding plastic melt intothe chamber [800] from opposed ends thereof. Feed means 83 is providedwith a feed inlet means 83a directing plastic melt substantially alongthe line of the dotted arrow 83c so that the melt entering through feedmeans 83 enters chamber 809. along one side thereof. Feed means 84 islikewise provided with an opposing feed inlet means 84a directing theplastic melt therein along a path indicated by the dotted arrow 84cwhereby the plastic melt in feed means 84 enters into the substantiallyopposed portion of the chamber [80a]. [Interior] The interior chamber[80a] is substantially equally divided by a centralized offset vane orguide means 87. Vane means 87 is provided with a base 870 mounted on [aninlet block] a main annular housing portion 79b (FIG. 5A) [means (notshown)] and the vane means 87 is offset a desired degree to provide apredetermined thickness relationship between the two plastic melts.Thus, vane means 87 divides the chamber [80a] into a plurality ofpassageways 85 and 86.

As shown in FIG. 5A the offset guide vane means 87 may be preset in aparticular location, such as shown at 87a and 87b to vary the ratio ofone plastic melt to the other. [As illustrated, a conventional (or onein accordance with the principles of the instant invention) inlet block90 is provided with an inlet block housing 91 and a die means 92.Mounted between the inlet block housing 91 and the die means 92 is theend-feed die plug 81. End-feed die plug 81 has an offset vane 87 mountedon appropriate base 870 having a feed inlet means 84a directing oneplastic melt along the path indicated by 84b and another feed inletmeans (not shown) directing the plastic melt along a path 83b asindicated by the dotted arrow] The plug 80 includes an outer housingportion 79a, through which the fastening means 82 are secured to theinlet housing (not shown), a main annular housing portion 79b, and theflow divider portion 79c. The flow divider portion 79c is comprised ofthe base 87c and the vane 87. Of course, it will be appreciated thatfeed inlet means 84a and [83b] 83a may be reversed so as to feed inopposing directions from that shown in the drawing, i.e. feed inletmeans 84a and 83a may be adjusted to feed into opposite sides of guidemeans 87. [into the upper portion of the die means 92 while feed inletmeans 83b may be adjusted to feed into the lower portion] Likewise, theguide means 87 may be offset in any desired position to yield an 80-20%thickness ratio or a 20-80% thickness of one plastic material to anotheras desired. It is contemplated that a plurality of such otfset die plugsbe provided for any desired ratio of the plastics utilized.

As will be appreciated, the [end feed] die plug means 80 can be readilyand easily removed without the necessity of cleaning out the entireextrusion apparatus or even the inlet block and one of the alternativeembodiments such as shown in FIG. 4, of the die plug may be insertedallowing efiicient and rapid transfer from a twolayer film manufacturingprocess to a three-layer film manufacturing process. There is no need toclean out the die means or the inlet block as the unique end feed dieplugs of the instant invention readily segment a two melt flow streaminto a two-layer or three-layer film as desired.

Referring now to FIG. 6 wherein an essentially side view of the inlethousing block 400 is shown. The inlet block [has a housing] 40a isprovided with a first feed means 41 and a second feed means 42 feedingtwo different or the same plastic melts into an inlet chamber 41awherein such different plastic melts form a segmented plastic meltsystem which is forced through an embodiment of an end-feed die plug 43substantially as explained hereinbefore. FIG. 6A illustrates the frontview of the inlet block 40' and it will be noted that the first feedmeans 41 feeds into the upper portion of end-feed die plug 43(substantially similar to the embodiment illustrated at FIG. 4) into thecentral or first passageway 51. while the second feed means 42 feedsmaterial substantially around the central passageway 51 into the outerpassageways 49, 49a. Central passageway 51 is provided with a throatstop means 51a preventing the material from feed means 42 from enteringsuch first passageway 51 and at the same time, preventing the materialfrom feed means 41 from entering the outer passageways 49, 49a. Theinlet block [40] 40a is also provided with a relatively short slopingoutlet feed passageway 44 substantially as explained in connection withFIG. 3 to allow the material along the outer passageways 49, 49a toreach the outlet slot of the die means (not shown) at substantially thesame time that the material from the central passageway 51 reaches saidoutlet slot. In this manner, substantially uniform layers of plasticmelt are formed substantially along the entire die means width so that agreater proportion of such film is useable and substantially less trimis required. This can also be seen in FIG. 7 using the die plug 60 shownin FIGS. 4, 4A, and 4B.

Thus, it will be seen that I have provided an improved [end-feed] dieplug and inlet block means for use with a plastic extruder which meetsthe objectives and advantages above set forth. The mechanism utilizes anadvantageous [end-feed] die plug and inlet block to provide a moreuniform multi-layer film structure which are readily adjustable for awide variety of films, provide ease of change over and maintenance andprovides advantages over structures heretofore available.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed but coversall modifications, changes and alternative constructions and methodsfalling within the scope and spirit of the principles of the invention.

I claim as my invention:

1. An end-feed die plug means for mounting in a plastic extrusionapparatus at a plastic melt inlet end of an end-feed die means, said diemeans having a desired width and an outlet slot extending in across-machine direction for extrusion of a film, comprising: a housingmeans having interior peripheral walls defining an interior chamber influid communication with said inlet end of said die means, a firstplastic melt feed means providing fluid communication to a first portionof said interior chamber, a second plastic melt feed means providingfluid communication to a second portion of said interior chamber, saidfirst and second portions of said interior chamber being spaced from oneanother, means supplying a plastic melt to said first and second plasticmelt feed means, and a guide means positioned within said interiorchamber in surface contact with at least a portion of said interiorperipheral walls and between said first and second portions thereof tosegment said chamber into at least two distinct plastic melts flowpassageways, said passageways guiding the plastic melt from said firstand second plastic melt feed means in adjacent contiguous flow streamsalong the width of said die means and toward said outlet slot, wherebythe plastic melt from the first plastic melt feed means forms a firstsubstantially uniform layer and the plastic melt from the second plasticmelt feed means forms a second substantially uniform layer of amulti-layer composite film.

2. An. end-feed die plug means as defined in claim 1 wherein the guidemeans is positioned between the first and second portions of theinterior chamber to segment said chamber into three distinct plasticflow passageways, said passageways guiding the plastic melt from thefirst and second melt feed means into adjacent contiguous flow streamsalong the width of the die means and towards the outlet slot whereby theplastic melt from the first plastic melt feed means forms a centralsubstantially uniform layer and the plastic melt from the second plasticmelt feed means forms a first outlet substantially uniform layer on onesurface of said central layer and forms a second outer substantiallyuniform layer on an opposite surface of said central layer so as to forma multi-layer composite film.

3. An end-feed die plug means as defined in claim 2 wherein the guidemeans comprise a substantially V- shaped gate positioned within theinterior chamber so that the first plastic melt feed means is positionedbetween the divergent portions thereof and the second plastic melt feedmeans is positioned substantially opposite the apex thereof.

4. An end-feed die plug means as defined in claim 3 wherein the V-shapedgate means defines an angle between the divergent portion thereof thatis substantially in the range of 15 to 135.

5. An end-free die plug means as defined in claim 1 wherein the guidemeans segments the interior chamber into plastic melt passageways havingpre-selected crosssectional areas that regulate the thickness of theplastic melts within each of said passageways.

6. An end-free die plug means as defined in claim 1 wherein the guidemeans is positioned to segment the interior chamber into a centralplastic melt passageway and two outer plastic melt passageways havingsubstantially equal cross-sectional areas, each spaced along oppositesides of said central passageway, said central passageway having asomewhat larger cross-sectional area than the cross-sectional area ofeach of said outer passageway.

7. In a plastic film extrusion apparatus having an endfeed die meanswith an outlet slot extending a desired width in a crossmachinedirection and a plastic melt supply feed means feeding a plurality ofplastic melts, and end-feed die plug means mounted on an inlet end ofsaid die means comprising, a housing having interior peripheral wallsdefining an interior chamber in fluid communication with said inlet endof the die means, a plurality of spaced apart melt feed means, eachpositioned to interconnect one of said plurality of plastic melts with aplurality of spaced apart portions of said interior chamber, and a guidemeans positioned within the interior chamber between said plurality ofspaced apart portions thereof in surface contact with at least portionsof said interior peripheral walls to segment said chamber into aplurality of distinct melt flow passageways, said melt flow passagewaysguiding the plastic melts from said plurality of melt feed means inadjacent contiguous flow streams along said die means and toward saidoutlet slot whereby each of said melts forms a substantially uniformlayer of a multilayer film.

8. In a multi-layer plastic film extrusion apparatus as defined in claim7 wherein the guide means is selectively positioned within the interiorchamber to predetermine the cross-sectional area of each of theplurality of melt flow passageways.

9. An end-feed die plug means for mounting in a plastic extrusionapparatus at a plastic melt inlet end of an end feed die means, said diemeans having an outlet slot extending in a cross-machine direction andhaving a longitudinal axis parallel to said direction for extrusion of amulti-layer composite film of a desired thickness, comprising, a housingmeans having interior peripheral walls defining an interior chamber influid communication with said inlet end of the die means, a firstplastic melt feed means attached to said housing means and providing afluid communication to a first portion of said interior chamber, asecond plastic melt feed means attached to said housing means andproviding a fluid communication to a second portion of said interiorchamber, said first and second portions being at approximately radiallyopposed. positions within said chamber. means supplying a plastic meltto said first and second melt feed means, and an adjustable guide meanspositioned in said housing means along a central axis thereof betweensaid first and second portions of said interior chamber in surfacecontact with at least portions of said interior peripheral walls tosegment said chamber into two distinct melt flow passageways extendingsubstantially parallel with said outer slots, said guide means havingguide surfaces positioned generally perpendicularly to said longitudinalaxes of said outlet slot, said melt passageways guiding the plasticmelts from said first and second melt feed means in adjacent contiguousflow streams along said die means and toward said outlet slot wherebythe plastic melt from said first melt feed means forms a substantiallyuniform layer and the plastic melt from said second melt feed meansforms another uniform layer of a multi-layer composite film.

10. An end-feed die plug means as defined in claim 9 wherein the firstand second portions are substantially parallel to radial axis of theguide surfaces and include oppositely offset guide portions extendinginto the interior chamber so as to direct the plastic melts from thefirst melt feed means toward one peripheral surface of the interiorchamber and direct the plastic melt from the second melt feed meanstoward an opposed peripheral surface of said interior chamber.

11. In a plastic extrusion apparatus having a plastic melt supply meansand an end-feed die means having an outlet slot extending in across-machine direction and having a longitudinal axis parallel to saiddirection for extruding a multi-layer composite film of a widthcommensurate with said outlet slot and of a desired thickness, thecombination of:

an inlet block member attached to said supply means for directing melttoward said die means, comprising, a housing means having an interiorinlet chamber, a plurality of melt feed means positioned within saidhousing means and providing a fiuid intercommunication between said meltsupply means and said inlet chamber, a first outlet means positionedwithin said housing means and providing a fluid intercommunicationbetween said inlet chamber and said die means, said first outlet meansproviding a relatively elongated melt flow path substantiallycommensurate with said outlet and extending substantially parallel withsaid longitudinal axes thereof, and a second outlet means positionedwithin said housing means and providing fiuid intercommunication betweensaid inlet chamber and said die means, said second outlet meansproviding a relatively short melt flow path defining an acute angle withsaid elongated fiow path and extending downwardly toward said outletslot whereby plastic melt passing through said second outlet meansreaches said die means prior to the plastic melt passing through saidfirst outlet means, and

an end-feed die plug means attached between said inlet block member andsaid die means, said plug means comprising a housing means havinginterior peripheral walls defining an interior chamber providing fluidintereommunication between said first and second outlet means and aninlet end of said die means, said first outlet means communicating witha first portion of said plug means interior chamber and said secondoutlet means communicating with a second portion of said plug meansinterior chamber, said first and second portions being spaced apart fromone another along the periphery of said plug means interior chamber, anda guide means positioned within said plug means interior chamber andbetween said first and second portions thereof in surface contact withat least portions of said interior peripheral walls to segment said plugmeans interior chamber into at least two distinct melt flow passageways,said flow passageways guiding the melts from said first and secondoutlet means in adjacent contiguous flow streams along the width of saiddie means whereby the melt from the first outlet means forms a firstsubstantially uniform layer and the melt from the second outlet meansforms a second substantially uniform layer of a multi-layer compositefilm.

12. An apparatus for extruding a multi-layer composite plastic film,comprising, a first melt supply means feeding a plastic melt at apredetermined volume flow rate, a second melt supply means feeding aplastic melt at a predetermined volume fiow rate, and inlet block meansattached to said first and second supply means, said inlet block havniginterior peripheral walls defining an inlet block interior chamber and afirst and second inlet block flow passageway in fluid communication withsaid first and second melt supply means respectively and withsubstantially opposed portions of said inlet block interior chamher soas to conduct the plastic melt from said supply means to said opposedinterior chamber portions an elongated die means attached adjacent tosaid inlet block means and having an outlet slot of a given widthextending in a crossmachine direction, said die means adapted to be influid communication with said inlet block interior chamber, a firstinlet block outlet means in fluid communication with said inlet blockinterior chamber and said die means, said first inlet block outlet meansdefining a relatively elongated melt flow path toward said outlet slotextending from said inlet block interior chamber to said die means alongthe elongated dimension thereof, a second inlet block outlet means influid communication with said inlet block interior chamber and said diemeans, said second inlet block outlet means defining a relatively shortmelt flow path extending downwardly toward said outlet slot andpositioned to define an acute angle with said elongated flow path, and aguide means mounted on said inlet slot adjacently between said first andsecond block outlet means and adapted to be in fluid communication withsaid die means, said guide means having generally divergent guidesurfaces in surface contact with at least portions of said interiorperipheral walls and extending toward said die means and generallyparallel with said outlet slots so as to divide each of said melt flowpaths into three distinct melt fiow sub-paths extending substantiallyparallel with said outlet slot, said divergent guide surfaces beingpositioned to define an angle therebetween ranging from about 15 to saidmelt flow subpaths guiding melt from said first and second supply meansin adjacent contiguous streams into said die means and along the widthof said outlet slot whereby a three-layer composite film havingsubstantially uniform layers throughout its width is formed.

13. In a plastic film extrusion apparatus having a die means with anoutlet slot extending a desired width in a cross-machine direction and aplastic melt supply feed means feeding a plurality of plastic melts, adie plug means mounted on an inlet of said die means comprising, ahousing having interior peripheral walls defining an interior chamber influid communication with said inlet end of the die means, a plurality ofspaced apart melt feed means, each positioned to interconnect one ofsaid plurality of plastic melts with a plurality of spaced apartportions of said interior chamber, and a guide means positioned withinthe interior chamber between said pluraliry of spaced apart portionsthereof in surface contact with at least portions of said interiorperipheral walls to segment said chamber into a plurality of distinctmelt flow passageways, said melt flow passageways guiding the plasticmelts from said plurality of melt feed means in adjacent contiguous flowstreams along said die means and toward said outlet slot whereby each ofsaid melts forms a substantially uniform layer of a multilayer film.

(References on following page) 13 14 References Cited 2,985,556 5/1961Rowland 425131 UK The following references, cited by the Examiner, are3,415,920 12/1968 at 425*131 UX of record in the patented file of thispatent or the original $448,183 6/1969 chsholm 425-13} X patent3,320,636 5/1967 Corbett 425 131 UNITED STATES PATENTS 5 3,471,89810/1969 Krystof 425-431 3,559,237 2/1971 Biggelaar et a1 425-131 11KILBY, JR p i Examiner 3,443,278 5/1969 Nauta 425-131

